Moulsford Railway Bridge

The original Moulsford Railway Bridge was built to carry the main line of the Great Western Railway (GWR) over the River Thames.[3] Construction of this truck line between London and Bristol had been authorised by an Act of Parliament in 1835, with construction commencing during the following year. The bridge, along with many of the railway's engineering features, was designed by the accomplished engineer Isambard Kingdom Brunel, who was the leading figure in the GWR's engineering and management.[3][4]

The bridge, which was built to carry a pair of broad gauge tracks, was a relatively ambitious design, consisting of four elliptical skew arches of 62 feet (19 m) span and a headway height of 21 feet 8 inches (6.60 m).[3] Consisting primarily of red brick with Bath stone quoins, it is skewed at an angle of 60 degrees to the river. The structure has often been regarded as being of an exceptional size for the era; to better accommodate such dimensions, Brunel incorporated a series of internal longitudinal walls and voids to lighten the superstructure, which also reduced the cost and time needed to construct it.[3] It has been alleged that the GWR had promised the Bishop of Durham to aesthetically embellish the bridge to mollify his doubts of the scheme.[5] Historic England has observed the bridge to be one of the most impressive structures along the whole length of the railway.[3]

Construction of the Moulsford Railway Bridge occurred between 1838 and 1840, having been built at the same time as several other railway bridges on the line, including those at Maidenhead and Gatehampton; furthermore, design features are shared between these three bridges.[3] Relatively little alterations have been performed to the structure since its original opening to traffic, even the construction of a second bridge alongside did not result in significant changes to the original bridge, the two structures remaining distinct separate identities. Since the building of the second bridge, the first has been often referred to as the 'west' or 'fast' bridge.[3]

Moulsford Railway Bridge from the upstream side, the newest is closest

The bridges from underneath; the original is closest

By the 1870s, capacity along the railway was becoming noticeably constrained by a lack of capacity, leading to pressure to widen the line wherever possible.[3] During 1892, the section of the line around the bridge was expanded to a quadruple track arrangement; to accommodate this, the construction of a second bridge was necessary. It was built alongside the upstream side of the original, being connected to it by a series of girders and brick bridgelets.[3][6] The two bridges are also joined together at the deck level by a series of vaulted brick footbridges.[3][7]

The design of the second bridge was, like many other structures built for the expansion, was intentionally designed to be sympathetic to Brunel's original bridge; thus, it shares many similarities, such as identical profile and dimensions, to the first bridge.[3] It also has several differences, such as the lack of stone quoins, while the plain uncut bricks form a jagged pattern where they meet the faces of the bridge. The second bridge is also somewhat narrower than the first, having been built to carry a pair of standard gauge tracks.[3]

In relation to the original bridge, it is often referred to as the 'east' or 'relief' bridge. The second bridge has typically been regarded as possessing less intrinsic merit than the first one.[3]